The general field of this invention is directed to the art of U-bolt saddle clamps which are employed for example in the exhaust system and elsewhere in automobiles and trucks powered by internal combustion engines. Clamps of this type also find utility in the building and construction industry for hanging of overhead pipes and also in the construction of tubular towers and antennas for example.
The known prior art directly concerned with such clamps is for the most part derived from a basic assembly comprising a U-shaped bolt that is threaded at its ends and has a generally semi-circular bight portion integrally connecting a pair of parallel legs which mount, in axially slidable relation, a sheet metal saddle member which member includes tubular portions that receive and house the bolt legs of the U-bolt, and which are connected by a central web portion extending transversely between the tubular housings and being integral therewith. The saddle has a work engaging edge facing which is arcuate and has the same radius as the U-bolt bight. Nuts are fitted on the threaded free end portions of the U-bolt legs which are then torqued against the adjacent ends of the tubular housing to bring the saddle and the bolt together for tightly clamping a pair of telescoped cylindrical tubes which are disposed between the bight of the U-bolt and the arcuate edge of the saddle member. On occasion, lock washers are interposed between the nuts and the ends of the tubular housings. In other applications, a hanger bracket of the type set forth in the copending application of John E. Heckethorn, Ser. No. 188,262, filed Sept. 17, 1980, now U.S. Pat. No. 4,372,017, is interposed between the top face of the saddle and the face of the nut members. In this manner, the entire assembly can be supported from the hanger bracket which is secured to the frame of the vehicle.
Typical examples of prior art structures of this general type are illustrated by Riker U.S. Pat. No. 2,719,345; Osborne et al U.S. Pat. No. 3,137,053; Heckethorn, U.S. Pat. No. 3,955,250; Downing, U.S. Pat. No. 3,729,782; and Heckethorn, U.S. Pat. No. 4,265,005. Additional examples of recent U-bolt clamp assembly patents are shown in Eisma, U.S. Pat. No. 4,056,869 and Wagner U.S. Pat. No. 4,183,122. In most of the prior art devices, the saddles are formed from initially planar oblong blanks formed of relatively thin sheet steel. The blanks are cut, stamped, rolled or otherwise formed to provide a central web connecting a pair of tubular portions which are arranged to slide axially on the legs of an associated U-bolt. In some of the patents, as for example Eisma and Wagner, the saddle web is formed of but a single sheet of material appropriately bent over to form additional thickness. In others, as for example Heckethorn U.S. Pat. No. 3,955,520 and Riker U.S. Pat. No. 2,719,345, the web is formed of a pair of substantially identical sheets joined in parallel face to face contact. In others such as Downing the web is formed from a single piece or several pieces of blank material folded to provide laterally spaced faces.
In modern usage especially in the automotive industry, the pipe-engaging edge of the saddle is required to impart sufficient clamping pressure on the telescoping pipe sections to which it is applied so as to indent a semi-circular bead therein. This bead prevents axial separation of the pipe elements. The applied clamping pressure is a function of the torque level to which the securing nuts are finally tightened when they are drawn up on the threaded ends of the U-bolt legs during assembly. It appears to be essential that there be some longitudinal reinforcement in the saddle member since tests have shown that in prior art clamps as in Riker where the saddle webs have no such longitudinal reinforcement the saddles will commence to twist laterally and roll over when tightened to torque levels approaching 20 ft/lbs. Of course, clamp saddles having longitudinally reinforcing means such as Downing et al successfully resist such twisting and rolling at much higher torque levels, as for example 30 ft/lbs. In recent years, even more rigid clamps have been developed as noted in Heckethorn, U.S. Pat. No. 3,955,250 and 4,265,005.
The trend in recent years has been to design clamps of this type which will withstand high torque values and yet which will result in economies of manufacture and in weight. Since four or more clamps are frequently used in a single vehicle, the economies to be achieved by even a slight reduction in cost and in weight may be significant.